1. Field of the Invention
This invention relates generally to the field of modem diagnostics and more particularly to a method and apparatus for providing modem side loopback capabilities in a two wire communication device (such as a dial up modem).
2. Background of the Invention
Loopback testing has long been provided as a mechanism for locating faults and impairments in telephone and data communication circuits. Loopback testing is generally described in CCITT recommendation V.54. Such loopback testing is normally accomplished by use of relays or the like to couple an output signal from a modem or similar device back into the input in order to simulate a complete communications path. By performing such loopbacks at various locations in the communication circuit, a fault or failure may be isolated to a line or device connected to the line.
Such loopback testing is commonplace in four wire data communications circuits where the loopback is accomplished by coupling one set of wires to the other. However, in a two wire circuit, it is difficult to accomplish loopbacks in all of the desired locations. The present invention addresses this difficult by providing a loopback capability which provides for looping back almost as far as the telephone line connection in a two wire modem.